Shock absorber



E. F. ROSSMAN Jan. 9, 1951 SHOCK ABSORBER Filed Aug. 6, 1947 I N VEN TOR.

BY guay, H/s

Patented Jan. 9, 1951 SHOCK ABSORBER Edwin F. Rossman, Dayton, `hio, assigner to General Motors Corporation, Detroit,y Mich., a

corporation of Delaware Application August s, 1947, serial No. 766,71;

7 Claims.

i l This invention relates to improvements in direct acting, hydraulic shock absorbers. A direct acting hydraulic shock absorber is one having two relatively movable portions and when applied to relatively movable sprung and unsprung masses, for controlling their actions has one of its relatively movable portions directly attached to the sprung mass and the other portion directly attached to the'unsprung mass.

It is among the objects of the present invention to provide a direct'acting, hydraulic, shock absorber with means for supercharging the working chamber, thereby maintaining full volumetric efliciency. This object is accomplished by providing the shock absorber with a spring loaded, floating piston in the reservoir space into which the piston rod displaced uid is directed upon the movement of the piston in one direction, the spring loaded piston returning such rod displaced fluid Vunder pressure to the working chamber upon movement of the piston in theopposite direction. Further objects'and advantagesrof the present invention will be apparent from the following description reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings: Fig-1 is a longitudinal sectional View of a direct acting hydraulic shock absorber equipped with the present invention. Y

Fig. 2 is a fragmentary sectional view of parts shown in Fig. 1, certain parts however, being illustrated in different relative positions in this figure.

Fig. 3 is a fragmentary sectional view of a direct acting.v hydraulic shock absorber equipped with a rvmodified form of the present invention.

Referring to the drawings and particularly to the Fig. l thereof the shock absorber is shown in fully collapsed position and comprises a cylinder 2B. One end of this cylinder telescopically receives a portion of the head member 2 i ,said head member being fitted. into the cylinder substantially to .prevent leaks at this point. A larger `diameter portion of the head member 2| is eX-. teriorly threaded so as to be screwed into the threaded end of a larger and surrounding tubular member 22. The annular space between the cylinder2 and the tubular member 22 provides a reservoir 23 for the shock absorber. For purposes of this description this may be termed the inactive reservoir. Any suitable sealing means 24 is clamped between the head member '2| and an abutment ring 25 so as to reduce and practically prevent fluid leaks past the threaded connection between the head member 2| and the tubular member 22j Head member 2| has a central opening in which the piston rod 26 is slidably supported. Said head member has a recess in its outer end surface'for receiving the packing gland 2l through which the piston rod 26 slidably extends' to the exterior of the shock absorber. Rod 25 has a disc 28 attached to its outer end and a mounting ring 29 is attached to the disc. This mounting ring 29 provides means for securing the relatively` movable portion including the piston rod 26 directly to one of the relatively movable members whose action the shock absorber is adapted to control.

Duets 30 are provided in the head member 2|, said ducts connecting the space in the recess, be-` tween the bottom thereof and the packing gland 2l, with the reservoir space 23 sothat any fluid tending to leak along the sliding connection be-l tween the pitson rod 2t and the head meriiber 2| may be returned to the reservoir 23. A disc 35 has a centralopening 3| (see Figi 2) and an annular recess 32 on one side, coaxial? of' said opening. 4The end of cylinder 2|) seats in this recess 32 and the diameter of the central opening 3i in the disc is less than the inside diameter of the cylinder so as to provide an annular shelf upon whichan element, to be described, rests. Tongues 36 extend vradially from the edge of the disc 35 to maintain it central of the tube 22. Disc 35 has a cylindrical extension 3l' which may be secured to the disc yin any suitable manner or it may be formed integrally therewith soV as to be concentric with the cylinder 2l). On the side of the disc. opposite the cylinder- 25, there is an an-y nular groove in V which a ring-shaped. resilient sealing and bumper element 35a is secured.

At the end of the tubular member 22 opposite the head member 2| there is attached a closure cup 33 secured to said tubular member in any suitable manner preferably by welding. Secured to the outer side of this cup 33 is amounting ring 39 which is utilized to attach the other relatively movable portion of the shock absorber to the other relatively movable member whose action it is intended to control. Within thiscup 38 there is provided a centralizingabutment member 4!) having a central annularup-turned flange l about which one end of a'coil spring .2 lits and rests upon. Radial fingers 14? eXtend"'from the central portion of this cehtrali'zing abutment member and fit the contour of the inner surface of the closure 'cup 28; The end ofthe cylinder 31 attached to disc ?''restsup'on the. radial fingers 43 thereby providing communication between the inside of the cylinder 31 and the annular space between it and the surrounding portion of the closure cup 38 and the tube 2:2. Thus it may be seen that the inactive reservoir portion 23 extends downwardly to the annular edge of the closure cup 38 then through. the; annular space betweeny said cupfand the cylinder 31 and then communicating with the interior of the cylinder 31 through the space between its edge and the bottom inner surface of the cup 38, provided by the radially extending ngers 43 of the centralizing abutment member 4D.

From the aforegoing it may befseengthat thcin.-A

terior of the cylinder 20 is in communication with the interior of the cylinder 31. there is provided a valve cage s tightly fitted in this cylinder and as shown in Fig. 1 resting uponv the annular shoulder provided by the recess 32 in 35 intor which the, cylinderV 20. extends. The valvecage.- has a.v central opening 5i surrounded by an annular ridge 52 on the inside of the. valve cage:facing the head member 2 l.` This annular ridge 52provides. aseatior the disc-valve53 yieldably urged uponsaid annular seat by inwardly extending radialgspring fingers; 5.4 secured within the-valvevcagee in any suitable man-ner.v A plurality ofv openings 55 are; provided in the valve cage arrangedfinacircular row around. the central.-,openings,-5l of saidcage. These openings 52 are.: normally closedby a, ring-.shaped disc-valve 554 which is predeterminately biased against an inwardly extending annular shoulder in the valve cage byf-the'spinning of the centralportion of the valvecage against.v the inner portion ofsaid discvalve.A As shown in Fig. 1- thedisc valve engages thee-side of the. valvecage, opposite the side engaged by valve 5,3 so that this disc valve acts oppositely from. the valve. 5,3. From the. foregoing it may be seen; that thisyalve cage mechanism normally separatesthe interiors. of the cylinders 2li and 31 the valve. 53` thereof beingoperative to permit-iluid'to-enter cylinder Uffrom cylinder 31 andthe valve 55 thereof being. operative to permit, fluidfrom cylinder@ to-enter cylinder. 31..

Within the cylinder 2l).` there. isA provided a pistonz titl.Y attached to. the. inner end of the piston rod 2B` sot asto be reciprocated thereby. This pistonhasa plurality ofl through` passages one group. being arranged in ak circular. row about another groupralsoa-rranged. in a circular row around the pistonrod. The passages 6 E inthe inner circular rowv are normally closed by a ling-shaped disc valve 52 clam-pecl betweenthepis-ton and a nut 63 which. secures the piston;4 to the pistonwrod. This ring-shaped, disc. valve 6?. may consistv of one or more ring shaped spring discs biased by the-nut 63 sofas to be pressed againstthe surface of the pistonv at a. predetermined pressure.v The passages 5L in the outerv annular row are normally closed; by a valve 6.54 urged against. the piston to closefsaid' passages; 34 by resilient spring. fingers (i6` formed on a ring clamped between a limiting retainer washer 511onthe piston rod and a washer ontherod between. valvespring- 85 and the adjacent valve. This valve 65. is apertured as-at- E3 whiolrpermits communication between the cylindenspace between the piston` 60 and head member Inthe cylinder 26. Y

2.1l andthe fluidpassageslinthe-piston. lroin this it. may be seen". that the piston isprovided with.valvedpassagesv adapted'to controlruid ow throughthe piston in either direction asthe pist0n. is; reci-procated. within the.A cylinder. The valve-65 provides for a substantially unrestricted fluid ow through the piston toward the cylinder space surrounding the piston rod 25 as the piston is moved away from the head member 2l while the valve 62 is operative to establish a restricted now of fluid in the opposite direction when the piston moves in the cylinder toward the head member 2i. For the purpose of identification, this piston Gamay be termed the positively actuated'piston.

A floating piston 1!) is provided in the cylinder 31. It has a central opening 1| in its head portion, surrounded by an annular ridge on the side of the-piston adjacent the valve cage 5D. A disc valve 'i2 is yieldingly maintained in engagement with the.Y annular ridge surrounding the central opening 1 byresilient fingers 13 extending radially inwardly from a ring secured to the piston 10 in anyl suitable manner. The coil spring 42 heretofore described as having its one end fitted upon the centralized abutment member 45 has its opposite endengaging the piston 15 and yieldably urges said piston toward the` disc 3.5" and into'contact with the sealing and bumper ring 35a.

Au bafe ring 3B is provided in the reservoirA space 23 the` inner annular edge ofthe said' ring being secured to the cylinder i',v the outer annu;- lar edge being spaced'iromtheinner annular suraceof the tube 22.

A guard tube 8l surrounds the tubular member 22. one end of. this. guard tube 81|. tting around andbeing attached to the disc 28 so as to move therewith.

Fig. 1y shows the shock absorber in the fully collapsed position. When due to separating movementsV of the members, not. shown, butto which the respective ringsA 29 and" 39 are adapted to be anchored', the piston 60 is moved in cylinder 2 0 toward the, head member 2l, iiuid Within the working Space 85 in the cylinder 20, having pressure exerted thereupon,- will' move valve 62 from. engagement with the piston to open pas,- sages 5l' and thereby permit thefluid to, pass from the chamber 85 through piston passages 5l into the cylinder working chamber 86;. between the piston andthe valve cage 50. The volume ofiiuid sov displaced will not be sufticient to ll this increasing space 85 between the piston 60A and the valve cage due to the presence of the rod. in chamber 85. and thus valve, 53 will be lifted from engagement with its annular valve seat 52 to permit fluid in the space 81 which for purpose, of' description may be termed the active reservoir, to ow through the` valve cage past the valvel 53 into the working space 8,6 above it. If the supply of fluid in the active reservoir 81 is insuiiicient to supply the necessary volume of fluid then valve 1,2 in piston 1E! will be lifted against the effect of spring lingersv 13 to permit, fiuid toflow from the inactive reservoir 23 and the. communicating space inside the cylinder 31 past valve 12 into the active reservoir and then through the valve cage 5,0 past its valve 5 3 intor the working space 85 directly beneath the piston 69. Valve 12 will not be lifted from itsseat unless piston 10 is engaged with the bumper ring IHa.`

When the movement ofV thev piston is reversed, pressure is exerted upon the fluid in the cylinder working chamber 85,. The duid pressure in cham.- ber B6 is directed against the valve 56 in the valve.- cage 55 and the valve 65 in the piston 60 to operate them and open their respectiveV iiuidA passages 55 and 64. A greater fluid pressure isaetessary to open valve 55 than valveP 65 soA that, the iirst flow of fluid from chamber 85, as the. plfcn Edmoves toward the, valve cage 5B, willbe through piston passages 64, past the valve into the cylinder chamber 85. Due to the presence of the piston rod 26 in the cylinder chamber 85, all of the fluid displaced from chamber 86 cannot be received by chamber 85, therefore the fluid displaced by said piston rod 26 will act upon valve 56 in the valve cage 50, to operate it and establish a restricted fluid flow through the passage 55 into the active fluid reservoir space 81. Fluid delivered under pressure to chamber 81 will move the floating piston 10 in the cylinder 31 downwardly toward the closure cup 38, Vagainst the effect of the spring 42.

The present shock absorber is so designed that the maximum volume of the active reservoir space 81 is at least equal to and preferably slightly larger than the maximum volume of the fluid that may be displaced by the piston rod 26. This prevents bottoming on the striking of the element 40 by the piston 10 as illustrated in the Fig. 2.

In use on automobiles, for which the present shock absorber is particularly designed, the piston 56 is rarely moved throughout the extreme limit of its travel and thus .the capacityof the active reservoir 81 might ordinarily be reduced, however, for safety sake and to render the shock absorber operative under al1 conditions, the active reservoir 81 is, as has been mentioned suiciently large to receive the maximum fluid displacement by the piston rod without moving the piston 1D against the bottom or end cup 38. As an added precaution openings 88 are provided in the wallof cylinder 31, so located that when the oating piston 10 reaches a predetermined position in its movement toward the closure cap 38, these openings will connect the active reservoir space 81 with the inactive reservoir 23 directly and thus permit excessive fluid, forced into the active reservoir space 81 to spill over into the inactive reservoir 23, thus limiting further movement of piston lil. When the movement of the piston 5Gv toward the valve cage 50 stops, said movement having been caused by relative approaching movements of the two members (not shown) between which the shock absorber is connected, the fluid, dis- -placed by the piston rod 26, will have moved the piston in a direction away from the disc 35 against the effect of spring 32. Now this piston 10 exerts a pressure upon the fluid in the active reservoir space 81. As a result, and upon the next movement of piston 50 away from the valve-cage y 50, this fluid in the active reservoir will be forced, under pressure of the spring loaded piston 18, into the working chamber 85, past the valve 53 in the valve cage. f

If, clue to internal leakage, the volume of fluid directed into the cylinder chamber 86 from the active reservoir 81 is less than the volume or fluid .displaced by the piston rod 26, the valve 12 will be operated, when the piston 16 engages the bumper ring 36a, permitting uid to be taken from the inactive reservoir'and directed through the active reservoir 81 into the working chamber 86. The amount of this fluid taken from the inactive reservoir 23 due to such leaking is substantially equal to the volume of uid lost from the cylinder content through said internal leakage and constitutes a iluid loss compensating supply whichy maintains the active fluid within the Vshock absorber at full volumetric eihciency resulting in a more eicient control by the shock absorber.

In the conventional shock absorber of this type and where constantly open orices are provided to 4obtain' a desired dampening effect, the iluid in the reservoir andthat in the Working chamber will 6 y seek a common level during inactivity. This tends toward the introduction of an undesirable amount of air into the cylinder working chamber which must be eliminated during shock absorber action before full eiliciency is attained. By sealing the cylinder against leakage by the use of the sealing ring 36a, this level seeking action is entirely eliminated even though the valves 62 and 56 are provided with ycomparatively large and constantly open orices.

`On the other hand, if, due to variable length, successive strokes of the shock absorber piston in opposite directions, the active reservoir 81 does not contain a Suflicient supply of fluid under presofv the piston 60, then valve 12 in the piston 10 will, when said piston 16 has reached its maximum up position by engaging the sealing bumper 36a, open to permit aflow of fluid from the inactive reservoir 23, through the active reservoir space 81 into the working chamber 86, thus supplying the additional uid to meet volumetric requirements.

Due to the shaking of the shock absorber during use, the iluid in theeinactive reservoir 23 becomes more or less aerated and aerated fluidY when taken into the working chamber of a shock absorber in any substantial amounts greatlyreduces the dampening effect of the shock absorber. However, with the present structure the compensating supply of fluid is of such small volume that only a relatively small-amount of aerated uid is present in the working chamber of'the cylinder, said small amount of aerated fluid havingan unappreciable eiect on the dampening eiciency of the shock absorber. "j

Fluid losses by internal leakage is substantially eliminated by the provisiony of the sealing and bumper ring 36a. After a period of rest and riormally the piston 6i? is midway between the head 2l 1 and valve-cage Eil, the chambers 86 and 81 lled reservoir space beneath the piston rlil.

with iiuid and the ilo-ating piston held in sealing engagement with the ring 35a by the spring 42. Very little if any fluid will leak into the inactive The sealing engagement of piston 'i6 with ring 36a, is especially advantageous to prevent loss of iluid from the cylinder during shock absorber inactivity when, as in some instances, valves 62 and 56 are provided with constantly open luid flow orifices.

In the Fig. 3 an alternate construction is illustrated. Here the cylinder 28 continues uninterrupted to rest upon the radial spacing fingersA 43 of the spring centralizing and abutment element t6. ThisV construction eliminates the provision of the disc 35 in the construction showny in Fig. 1 and the tube portion 3'! is Ynow provided by a continuation of the main cylinder 2i). shock absorber construction of Fig. 3 is identical with that shown in Fig. 1 and functions in a like manner.

In either one of these constructions the shock absorber is provided with two fluid reservoir portions, that is the inactive portion 23 lincluding also the portion inside the tube or cylinder portion 31 and the'active reservoir portion between the piston 1D and the valve cage 5S. The active reservoir portion directly supercharges the working chamber of the cylinder with fluid during operation of the device, the inactive reservoir portion on the other hand simply adds fluid to the active reservoir portion in case of a reduction of the .necessary volume of uid therein due to interior leakage. While thembydment of the present. inverni@ Otherwise, the

7 as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. A hydraulic shock absorber comprising a cylinder having a closure member at each end; a two-way valve mechanism secured in the cylinder and dividing it into two compartments; a piston in the one compartment, attached to a rod slidably extending through the one closure member, said piston having valved passages providing for controlled duid flows through the piston in either direction; a floating piston in the other cylinder compartment, having a valved port providing for the flow of fluid only into the space between the floating piston and the valve mechanism; a spring interposed between the floating piston and the other, more adjacent closure member; a fluid reservoir in communication with the cylinder space occupied by the spring; and a normally ineffective opening in the cylinder, said opening being rendered eective to permit uid to flow from the space between the floating piston and the valve mechanism and into the reservoir, when said floating piston is moved a predetermined distance from said valve mechanism.

2. A hydraulic shock absorber comprising a cylinder having a closure member at each end; a valve mechanism secured in the cylinder and dividing it into two compartments, said valve mechanism being operative to establish a substantially free iiow of fluid in one direction and a restricted Ilow in the other direction between said compartments; a piston in each cylinder compartment, the one piston being positively reciprocated in its compartment and having valved passages certain of which are operative to establish a substantially free flow of fluid through the piston in one direction, the other a restricted flow in the opposite direction; the other piston having a valved port operative to permit a flow therethrough in one direction only, said other piston being actuated away from the valve mechanism by fluid pressure; a spring urging said; other piston toward said mechanism; a fluid reservoir connected with the cylinder compartment on the side of said other piston engaged by the spring; and an opening in the wall of the cylinder and operative to provide communication between the reservoir and cylinder compartment between said other piston and valve mechanism only when said other piston has been moved a predetermined distance from said valve mechamsm.

3. A hydraulic shock absorber comprising a' cylinder divided into two working chambers by a piston attached to a rod which extends through and is slidably supported by a head member in oney end or the cylinder; a fluid containing reservoir; a spring loaded, apertured partition, dividing the reservoir into two compartments onelof which is in direct communication Ywith one workfing chamber of the cylinder, a valve normally closing the aperture in the partition and operative to establish fluid flow from the one reservoir compartment into the reservoir compartment directly in communication with the cylinder; a two-way valve mechanism interposed between the said one working chamber of the cylinder and the reservoir compartment directly connected therewith, said valve mechanism being operative to establish a substantially freeflow of nuid into said working chamber and a restricted` flow of fluid from said chamber in responseto movements of the piston away from and toward said valve mechanism respectively; valved passages in the piston for establishing fluid flows therethrough in either direction; and a normally inactive opening in one part of the reservoir, said opening being rendered active by movement of the oating piston into a predetermined position relatively to said valve mechanism, for directly connecting the two reservoir compartments.

4. A hydraulic shock absorber comprising 'two centrally aligned cylinders; a coupling ring securing the adjacent ends of said cylinders together; a piston'in the one cylinder having a rod attached thereto, said rod slidably extending through a head member at the end of said one cylinder, said piston having valved vpassages providing for the transfer of iluid from one side of the piston to the other as said piston is reciprocated; a floating piston in the other cylinder,- having a port normally closed b-y a valve to prevent fluid from flowing from the space between the two pistons through said port; a spring yieldably urging the floating piston toward the coupling ring; a fluid containing reservoir in communication with the end of said other cylinder opposite the coupling ring; a Valve mechanism between the two pistons, operative to establish a substantially unrestricted iiuid now from the space between said mechanism and the iioating piston into the space between said mechanism and the other piston as said other piston moves away from said mechanism and to establish a restricted flow of fluid in the opposite direction as said other piston moves toward the iioating piston; and an opening in said other cylinder rendered operative to connect the space between the floating piston and the valve mechanism with the reservoir, only when said floating piston has been moved a predetermined distance from said valve mechanism.

5. A hydraulic shock absorber comprising a cylinder having a closure member at its one end, through which a rod slidably extends; a piston in said cylinder, attached to the rod and having valved passages providing for the controlled transfer of lluid from one side of the piston to' the other as the piston is reciprocated; a flange `ring attached to the cylinder at the end opposite the closure member; a valve mechanism in the cylinder supported by the ring, said valve mechanism being operative to establish a substantially free ow of iiuid into the cylinder as the piston moves away from said mechanism and a re'- stricted flow from the cylinder as the piston moves toward said mechanism, a tubular member having one end attached to the ring; a iiuid containing reservoir in communication with the other end of the tubular member; a floating piston in said tubular member, said piston having an opening surrounded by a valve seat on the side of said floating piston adjacent the valve 'mechanism; a valve yieldably urged to close said opening; a spring yieldably urging the floating piston toward the ring; and an opening in the side of the tubular member operative to connect the reservoir and the interior of the tubular member above the valve of the floating piston, only when the floating piston reaches a predetermined position relatively to the valve mechanism.

6. A hydraulicshock absorber comprising, two cylinders joined together, each having a piston therein, the "one piston in the first -cylinder being secured-to arod slidably extending-through lazsefz'fies a head member at the outer end of the rst cylinder, the second, floating piston in the second cylinder being yieldably urged toward the first cylinder by a spring interposed between the second piston and a cover cap of the second cylinder, the said one piston having valved passages providing for the transfer of lluid from one side of the piston to the other as said piston is actuated by the rod, the second piston having a valved port providing only for the flow of fluid into the space between the two pistons; a valve mechanism interposed between the two pistons, said valve mechanism providing for a substantially free flow of fluid from the space between said mechanism and the floating piston into the space between said mechanism and the rst piston as said rst piston moves away from said mechanism and providing Vfor a restricted fluid flow in the opposite direction through said mechanism as the first piston moves toward said mechf anism; a tubular member surrounding` both cylinders, the ends of the tubular member being secured respectively to the head member and end cap of the two cylinders, said tubular member providing a uid containing reservoir which is in communication with the second cylinder at its end cap end; a normally ineffective opening in the wall of the second cylinder, said opening being rendered effective to permit fluid in the space between said valve mechanism and the lloating piston to enter the fluid reservoir when said floating piston is moved a predetermined distance away from said valve mechanism.

'7. A hydraulic shock absorber comprising in combination, a cylinder; a two-way Valve mechanism xed in the cylinder and dividing it into two compartments; a reciprocative, valved piston in each compartment, one piston being positively actuated, the other being spring loaded and actuated in one direction by fluid pressure resulting from the movement of the said 'one piston in a directiongtoward the Valve mechanism; a fluid supply chamber in constant communication with the cylinder compartment beneath the spring loaded piston; and means rendered effective by movement of said floating piston into a predetermined position to relieve the pressure in the cylinder space above said oating piston by connecting itdirectly with the fluid supply chamber.

EDWIN F. RossMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Y Date 2,126,880 Gardner Aug. 16, 1938 2,327,295 Whisler Aug. 17, 1943 2,360,755 Boor Oct. 17, 1944 

